Electric drive units are coming into use in a great variety of applications. For example among motor vehicles, the use of low-emission vehicles that derive at least a portion of their main drive energy and/or energy for auxiliary drives from electrical sources, is ever increasing. Typical electric drive units comprise an electric motor for providing the electrical drive power, and an electronic module for controlling and monitoring the operation of the electric motor, for example for regulating the rotational speed and output power of the electric motor.
Such electric motors, due to their high power density, must be cooled during operation and therefore are typically equipped with a cooling circuit, which is usually a water cooling circuit that uses flowing water as a cooling medium. One way of providing the water flow passages necessary for the cooling circuit, is to provide the electric motor with a double-walled housing that forms a water jacket which allows the cooling water to flow through passages arranged between the outer wall and the inner wall of the motor housing.
An electronic module for controlling and monitoring the electric motor generally includes a plurality of different functional units, such as a power unit and a control unit, for example. The electronic module is arranged as a separate and independent module that is located spaced away from or separate from the electric motor. Generally, at least one of the functional units included in the electronic module (e.g. the power unit) has a high power dissipation and must therefore be correspondingly cooled. In order to provide the necessary cooling, i.e. to carry away the dissipated heat, the electronic module conventionally includes its own separate cooling circuit that is connected in series with the cooling circuit of the electric motor by means of coupling hoses or the like. Additionally, external signal conductors and power supply cables are connected between the electronic module and the electric motor for conducting sensor signals and control signals as well as the power supply voltage between the motor and the electronic module. These external connection lines are typically embodied as cables having connector plugs connected to corresponding sockets provided on the electronic module housing and on the electric motor housing.
Several disadvantages arise from such a structural arrangement of the conventional electric drive unit with the electronic module separated from the electric motor, and especially with separate cooling circuits and external cable connections for the electric motor and for the electronic module. First, the necessary connections between the electric motor and the electronic module for achieving the overall cooling, the signal transfer, and the power transfer to realize the complete electric drive unit become complicated and give rise to problems with regard to reliability, durability, aging, wear and tear, and seal leakage problems in the coupling hoses and cables between the electric motor and the electronic module. Secondly, the surface area required for mounting the components and therewith also the total structural volume of the electric drive unit is increased. Thirdly, the assembly of the electric drive unit is rather complicated and leads to relatively high manufacturing costs.